1. Field of the Invention
The present invention relates generally to a loopback device for use in a Fiber-to-the-Premises (FTTP) optical network, and more specifically, to a loopback device utilizing bend insensitive optical fiber to facilitate deployment of a connectorized distribution cable through a small-diameter conduit.
2. Technical Background
Optical fiber is increasingly being used to deliver voice, video and data transmissions. In this regard, fiber optic networks have been developed to deliver Fiber-to-the-Premises (FTTP), Fiber-to-the-Curb (FTTC) and Fiber-to-the-Subscriber (FTTS), collectively referred to as “FTTx networks.” The most recently developed of these FTTx networks typically include distributions cables that originate from a central office and extend outwardly along a main route in aerial and/or buried installations. At various locations along the length of these distribution cables, optical fibers are severed (pre-terminated) from the distribution cable and routed separately away from the distribution cable to provide branches off of the distribution cable, referred to herein as “tap points,” “mid-span access locations,” “branch points” or “tether attach points.” At these tap points, pre-terminated optical fibers of the distribution cable are often spliced or otherwise optically connected to a length of optical cable referred to herein as a “tether.” The tether is used to provide optical fiber to an optical network terminal (ONT), network interface device (NID) or other optical connection terminal located along the distribution cable within reach of the tether. Tethers may also be used for mitigating span length measurement issues resulting from errors in pre-engineered cable assembly installations.
At the downstream end of each tether, one or more optical fibers optically connected to the optical fibers of the distribution cable are typically terminated to a multi-fiber ferrule. As the branched optical fibers are needed for service, the multi-fiber ferrule end of the tether is routed to a predetermined location and optically connected to the ONT, NID or other optical connection terminal in a known manner. Tether cable ferrules that have not yet been connected into service are typically protected and environmentally sealed using a dust cap that keeps the ferrule free of contaminants and protected from physical damage.
In the past, in order to test the optical continuity of optical fibers originating at a central office that pass through a tap point and terminate at a multi-fiber ferrule, it was necessary for a field technician and/or optical signal detection equipment to be physically present at the end of the tether in order to measure signal strength or loss through the total length of optical fiber. This time consuming procedure results in increased deployment costs in FTTx networks. Further, by having to measure signal strength and loss at the physical downstream location, it is often necessary to remove the dust cap in order to provide access to the ferrule, thus exposing the ferrule to contaminants and potential physical damage.
Accordingly, what is needed is a device that makes it possible to measure signal strength or loss along a length of optical fiber, including along a length of spliced together segments of optical fibers, without the need for a field technician and/or optical signal detection equipment to be physically present at the downstream end of the fiber. Further, what is needed is a device that enables a service provider to measure signal strength or loss in a length of optical fiber from the upstream end of the fiber at which an optical signal originates. Still further, what is needed is a device adapted to be deployed along with a pre-engineered fiber optic distribution cable that allows for signal strength or loss to be determined at the upstream end of a length of interconnected optical fibers while providing protection for a connectorized downstream end during installation, and until the connectorized end is needed to provide service. Such a device is preferably provided for each multi-fiber connector within an FTTx network. A desired device would include bend insensitive optical fiber to facilitate deployment of a connectorized distribution cable through a small-diameter conduit, such as a cable conduit having an inner diameter as small as about 1.25 inches.